Device for removing investments from sectional dental flasks



June 3,1941. ,5 J, FRANWlcK v 2,243,950

DEVICE FOR REMOVING INVESTMENTS FROM SECTIONAL DENTAL FLASKS Filed June26, 1939 2 Sheets-Sheet 1 E. J. FRANWICK ,243,950

June 3, 1941.

DEVICE FOR REMOVING INVESTMENTS FROM SECTIONAL DENTAL FLASKS 2Sheets-Sheet 2 Filed June 26, 1939 I l'dzrzaitd Fara/2A), p Inv mfar .59I56 45 -11 (2% M1,

Patented June 3, 1941 UNITED STATES NT OFFICE DEVICE FOR REMOVINGINVESTMENTS FROM SECTIONAL DENTAL FLASKS Application June 26, 1939,Serial No. 281,183

9 Claims.

My invention relates to a device for removing investments from dentalflasks. Heretofore, after investing a case with plaster of Paris andcuring the case in a dental flask, it was necessary to gouge out theplaster from the flask and at times subject the investment to severeblows by means of a hammer or other instrument in order to loosen theinvestment from the flask. This was particularly true due to the factthat the inner surface of the flask is usually more or less rough orirregular, and also because of the fact that the proper tapers had notbeen provided.

Although flasks heretofore used have been made in sections, they couldnot be easily separated for reasons stated, and their construction madeitexceedingly difiicult to separate the sections. because of the bondingof the investment to the sections.

One of the objects of myinvention is to provide what I term an ejectorfor use in connection with flasks, the flask proper being arrangedwithin a suitable frame or support and means provided to easily loosensections of the flask so as ,to permit of a convenient separation,allowing the investment to be withdrawn as a complete unit.

Another object of my invention is to provide an ejector frame or supportfor removing investments from flasks to be used in association withprying elements, and to equip said frame or support with means to enablesaid prying elements to be fulcrumed thereon so as to exert pressureagainst parts of the flask for the purpose of loosening the investmentfrom the flask.

A further object of my invention is to provide the ejector frame orsupport with openings so positioned with reference to depressions ornotches formed in the flask that upon inserting prying elements throughsaid openings and entering the inner ends thereof in said depressions ornotches, pressure applied to said prying elements, while using one ofthe walls of each of said openings asa fulcrum point, will quicklyloosen the sections of the flask from each other and from the investmenttherein while both are retained within the frame or support.

A still further object of my invention is to so construct the flask thatthe sections thereof can be easily removed from the investment.

With the above and other objects in view, my invention consists inassociating a sectional flask with my improved ejector means, which whenbrought into use will quickly and efliciently separate the sections ofthe flasks so as to permit of plete unit.

The invention also consists in associating a sectional flask with aframe or support in which said flask is held and which frame or supportis adapted to have associated therewith means for coaction therewith andwith the flask to cause separation of the sections of the flask andthereby separate the investment in the flask from the sections thereof.

The invention further consists in the novel features of construction andin the arrangement and combination of parts to be hereinafter describedand more particularly pointed out in the subjoined claims.

In the drawings Fig. 1 is a side elevation of my improved ejector typeflask, the flask being shown inverted in the frame or support and havingthe upper section or cover of the flask removed.

Fig. 2 is a rear elevation of the flask and the frame or support. I

Fig. 3 is a plan view of the same.

Fig. 4 is a perspective view of the frame or support in which the flaskis to be retained when the upper section or cover of the same isremoved.

Fig. 5 is a vertical longitudinal section taken 'on line 55, Fig. 2.

Fig. 6 is a horizontal section taken on line 6-6, Fig. 1, looking up.

Fig. 7 is a vertical section through a portion of the flask taken online 'l'l, Fig. 9, a portion of the investment being shown.

Fig. 8 is a vertical section taken on line 8--8, Fig. 9 showing theinvestment in the flask preparatory to curing the case.

Fig. 9 is a perspective view of the flask proper.

Having reference to the drawings in detail, Ill designates the ejectorframe or support utilized to receive therein a portion of the sectionalflask I I. This frame or support comprises a base 12 having an elevatedportion 13 conforming somewhat to the outline of the flask, butpreferably smaller than the latter, and rising from the base are twoopposite uprights or posts [4 connected by a cross bar l5 at a distancespaced from the elevated portion 13 of the base somewhat greater thanthe height of the flask portion to be used in connection with this frameor support. Formed medially on said cross bar is an enlargment or headI6 from which rises a boss ll. The enlargement or head I6 is made hollowon its underside, as at i8, to receive a pressure element IS in the formof a disk swiveled to the lower end of a pressure screw 20 threadedthrough the boss I l1 and the upper wall of the enlargement or head 1It. For conveniently operating the pressure screw, it is provided with aknurled head 2| at its upper end.

Extending from diametrically opposite points of the enlargement or head[6 and the boss I! and arranged at right angles to the cross orconnecting bar are arms 22 having at their outer ends upstandingportions 23 and these arms are webbed to strengthen the same and givethem a symmetrical appearance. The upstanding portions 23 terminate inthe plane of the upper ends of the uprights or posts M, and when theframe or support is reversed, as may be found desirable at times, saidupright portions and uprights or posts serve as legs for the device.-

The elevated portion l3 of the base is provided with screw holes 24 (oneonly being shown in Fig. l) by means of which the frame or support canbe conveniently fastened to a table or other foundation. In the uprightsor posts l4 openings 25 are arranged, the purpose of which will appearhereinafter. The ejector frame or support It with its several integraland associated parts may be termed holding means or supporting means inits broadest sense, although more specifically it may be termed anejector or flask-stripping frame. a

The flask proper is formed in three sections; one 26, which I term thelower section or member; the second 27, referred to as an intermediatesection or member; and the third 28, which may be called the uppersection or member, but which in reality is a comparatively flat memberand may be more particularly referred to as the cover of the flask. Theflask may be described as particircular in formation in that it hasalmost a cylindrical form, and at one side it is provided with asubstantially straight-lined heel portion 29 which may be said to cutoff a sector of a cylinder.

proaches the parti-cylindrical portion of the perimeter of the flask.The parting lines of the sections or members are designated by thenumerals 3E, 32, and the intermediate section or member 27 of the flaskis provided at these partof said intermediate section and theseprojecting ends are comparatively long. The upper ends of the dowel pins33 and enter dowel openings 35 inthe upper section or cover, while thelower ends thereof enter dowel openings 36 in the lugs of the lowersection or member. In this manner the sections are caused to register sothat the exterior of the flask is perfectly flush at the parting lines3! and 32 and the interior surfaces of the walls of the sections ormembers are preferably alinedat all points within the flask. Theintermediate section or member 21 has the inner surfaces of its wallsflared downwardly, as at 31, while the lower section or member '26 hasits inner surfaces flared upwardly, as at 38.

To'assure easy and perfect assembly'of the flask sections and to directthe ends of the dowel pins 33 and 3d properly into the dowel openings 35and 3B of the upper and lower sections, the extremities of these dowelpins are tapered as shown at 33 and 3 3, the tapers 33 being at the Eachof the sections has lugs 30 at the a points where the straight-linedportion ap-' upper end of the dowel pins and the tapers 34 at the lowerends thereof. The major portions of the dowel pins 33 and 34 and thedowel openings receiving the projecting ends thereof are cylindrical.The lower ends, however, of the dowel openings 35 are flared, as at 35while the upper ends of the dowel openings 36 are flared, as at 36 Thetapers at the upper ends of the dowel pins are comparatively short, andthe cylindrical portions of said pins adjacent said tapers rise abovethe flared lower portions of the dowel openings 35 and fit snugly withinthe cylindrical upper portions of said dowel openings. The tapers at thelower ends of the dowel pins are somewhat longer, due to the fact thatthe dowel openings in the lugs of the lower section of the flask arecomparatively long, but the cylindrical portions of said pins adjacentsaid tapers extend beneath the flared portions of the dowel openings 36and fit snugly within the cylindrical lower portions of said dowelopenings. It will be understood, therefore, that by tapering theextremities of the dowel pins and providing the dowel openings 35 and 36with flared portions, the pins will be easily guided into theirrespective receiving openings in the upper and lower sections of theflask, and assurance will be had of a perfect alinement of the flasksections.

The flask is shown in its normal position in Fig. 9 of the drawings, andwhen preparing the investment it is so positioned, the model or case,designated by the numeral 39, is placed within the lower section of theflask after separating the sections thereof. This model or casecomprises the usual stone mounting 49 on which is built a wax ridge 4|havingportions of artificial teeth 42 embedded therein. 7 The stone orother mounting is molded or formed to a thickness conformingapproximately to the height of the surrounding walls of the lowersection so that its upper surface is in horizontal alinement with theup- 7 ing Ali-is then coated with a separating medium,

such as soapstone or other like'material, after which the intermediatesection or member 21 is seated on the lower section or member. Thisintermediate section or member is then filled with plaster of Paris inplastic form or some other similar material, as shown at 44, completelycovering the model or case. The plaster of Paris is then leveled offeven with the upper edge of said intermediate section or member. Thesetwo plastic masses, one within the lower section and the other withinthe intermediate section of the flask, form the investment for the modelor case. The upper section or cover is then placed upon the intermediatesection and over the second mass of plaster of Paris within theintermediate section, and it has one or more holes 45 formedtherethrough into which a small quantity of plaster'of Paris in plasticform is to be placed so as to become bonded with the plastic materialwithin the intermediate section of the flask. 7 To assure a good bondingat these'points the walls of said holes are flared outwardly and 'aretcbe filled in before the plastic material within the intermediate sectionbecomes set.

Up to this point there has been provided an investment with a partingline 46 between the two portions 43, 44 of the investment, thepartingline of the investment of course being coincident with the parting line32 between the intermediate and lower sections of the flask.

The flask thus prepared is placed in boiling water, at which time thewax ridges 4| become fluid and the wax oozes out, at least in part,through the parting line 46 of the investment and the parting line 32 ofthe flask. The flaskis then opened and the opposing surfaces of the twoinvestment portions 43 and 44, as well as the upper surface of the stonemounting 40, are then washed with hot water so that all wax and theseparating medium previously employed are disposed of. The teeth willnow be held in position by the investment portion 44 within theintermediate section. The wax originally within this investment portion44 having been disposed of, a groove is formed of the exact formationwhich the wax ridges originally had, the teeth projecting with theirroot portions downwardly into said groove. This groove is then packedwith a vulcanizable or curable material, and the intermediate section ofthe flask having the investment portion 44 is again placed upon thelower section with its investment portion 43, the registering dowels onthe flask bringing the two sections together in the same relation asthey had when the investment was being prepared. The upper section orcover is then placed upon the intermediate section and the case cured inany approved man- While the method of procedure thus far described formsno portion of my invention, it is believed necessary to describe suchprocedure in order to have a clear understanding of the use andadvantages of my invention.

As hereinbefore stated, it has been a difficult matter to remove theinvestment from the flask, and in gouging out the plaster material fromthe flask or subjecting the investment to blows by .the use of a hammeror other instrument in order to break or shatter the same while withinthe flask, the denture thus created from the model or case often becomesbroken, with the result that the entire operation steps referred to mustagain be repeated.

By the use of my ejector or flask-stripping frame in association withsuitable flask-removing means, separation of the flask from theinvestment can be easily effected. With this end in View the uppersection or cover 28 is removed from the flask, and the remainder of theflask with the investment therein is reversed and positioned within theframe, or flask holder as it may be termed. So positioned, it issupported on the elevated portion l3 of the base, the plaster of Parisinvestment only being in contact with said elevated portion, asclearly-shown in Fig. 5. The bottom wall of the lower section thereforeis at the top, as clearly shown in said figure. This bottom wall isprovided with a large opening 41, preferably circular, counterboredinwardly to form an inwardly opening shoulder 48, said opening beingclosed by a holding element 49 whose edge is rabbetted to fit saidcounterbored opening and thus permit movement of the lower sec tionoutwardly or upwardly while retaining said holding element against theinvestment and the stone or other mounting provided for the denture,

With the flask'so positioned, the pressure element I9 is held tightlyagainst what is now the top of the inverted portion of the flask andmore particularly against the holding element 49 by manipulating thepressure screw 20. The flask minus its top section or cover is nowfirmly clamped within the frame or support with the investment havingthe denture embedded therein, as clearly shown in Fig. 5. The lowersection 25 of the flask is provided at its upper edge with notchesordepressions 50, one notch being preferably arranged at the heel portionof the flask and the other at a point diametrically opposite so thatthese notches or depressions are in line or substantially in line withthe openings 25 in the uprights or posts 14. It is of course understoodthat the notches or depressions could be as well formed in the loweredges of the intermediate section 21. The uprights or posts are providedwith lateral extensions 5| at opposite edges in line with the openings25 therein, which not only provide added strength for theseuprights orposts where weakened by such openings, but the extensions of one of saidposts are utilized to properly position the flask within the frame orsupport, since the lugs 30 of the flask are intended to be positionedagainst the inner sides of said last-mentioned extensions, as best shownin Fig. 3. So positioned, the investment only lies in contact with theelevated portion I3 of the base, while the walls of said intermediatesection are located outside the area of said elevated portion, for apurpose to presently appear.

52 designate prying elements in the form of flat bars which are insertedthrough the openings 25 in the uprights or posts l4 and have their innerends reduced in thickness, as at 53, so as to enter the notches ordepressions 50 in the lower section 26 of the flask, as clearly shown inFig. 5. With the prying elements or bars 52 so positioned and theholding element 49 forced against the investment by the pressure screw20, it is only necessary to exert pressure downwardly on the pryingelements or bars while utilizing the lower walls of the openings 25 inthe uprights or posts as fulcrum points for said prying elements or barsto cause the lower section of the flask to be moved or stripped upwardlyfrom,

the investment therein to the position shown in .dotted lines 54 in saidfigure, said movement beelements or bars 52 upwardly, whereupon theintermediate section 2'! is forced downwardly within the frame to assumethe position shown in dotted lines 55 in Fig. 5, this being permitteddue to the fact that the inner surface of the peripheral wall of saidintermediate section is flared downwardly when the flask is in normalposition. It will thus be seen that although the investment becomesfirmly bonded to the walls of the flask during the act of curing thecase or denture, with my improved invention the flask can be quickly andeasily separated therefrom. Upon loosening the pressure screw andloosely repositioning the flask sections over the investment, the flaskwith the investment loosely therein can be easily withdrawn from theframe or support, after which the investment can be withdrawn from theflask and broken or cut away without any possibility of breaking thedenture therein, the latter being easily stripped from the stonemounting so that after a thorough cleansing, it is ready for fittingwithin the mouth of the patient.

In some instances it may be found desirable to invert the frame orsupport so that it rests upon the upper ends of the uprights or posts [4and upon the upstanding portions 23 of the arms 22. At such times bothuprights or supports and the upstanding portions 23 serve as legs, andwhen so positioned the sections 26 and 21' can be stripped from theinvestment by exerting pressure successively in opposite directions onthe prying elements or bars 52. This reversal of the frame or supportmay by some be considered desirable, particularly when the frame orsupport is not fastened to a table or other foundation.

It will be apparent that the frame or support with the prying elementsor bars provide a convenient stripping device for stripping the sectionsof the flask from the investment and that the investment can be brokenor cut away from the denture while free of any surrounding object, thusmaterially minimizing the chances of injuring the denture in the act ofremoving it from the investment; at the same time enabling such removalwithin a small fraction of the time and with less care than is now foundnecessary under present day methods.

Where in the claims reference is made to a flask or sectional flask, itis intended to include a flask in which an investment is entirelyenclosed, or in Which a portion of the flask is removed and a portion ofthe investment exposed.

Having thus described my invention, what I claim is:

1. A device for removing investments from sectional dental flasks,comprising holding means 'to engage and hold the investment immovablytherein While within said flask, and means provided on said holdingmeans to permit a pry to be fulcrumed thereon for separating thesections of the flask and freeing the investment therefrom whileretained immovably in said holding means.

2. A device for removing investments from sectional dental flasks,comprising supporting means provided with means to retain the investmentimmovably within said supporting means while 1 within said flask andwith means to permit separation of the sections'of said flask underprying action of suitable elements fulcrumed on said supporting meanswhile said investment is immovably retained within the latter.

3. A device for removing investments from sectional dental flasks,comprising supporting means to immovably clamp the investment within theflask while allowing clearance space for movement of the sections ofsaid flask, and means embodied in said supporting means serving asfulcrum points on which prying elements are adapted to be fulcrumed forloosening the sections of said flask from said immovably clampedinvestment and for moving portions of said sections into said clearancespace.

4. A device for removing investments from sectional dental flasks,comprising supporting means for said flask including elements atopposite'sides of said flask, means to clamp said investment at the topand bottom within said supporting means while retaining said flasksections in unclamped condition, said elements being provided with meansfor association therewith of prying means utilizing said elements toprovide fulabove said flask and extending across the latter,

'crums therefor, said prying means being adapted to engage the sectionsof said flask and exert force thereagainst to strip the same from saidinvestment while the latter is clamped.

5. A device for removing investments from sectional dental flasks,comprising a stripper frame for a flask having a base upon which theinvestment within said flask rests and an upright rising from said baseprovided With a bearing point adapted for association with a pryingelement designed to engage the sections of said flask while utilizingsaid bearing point as a fulcrum to exert force against either or bothsections of said flask and strip at least one of said sections from saidinvestment. 7

6. A device for removing an investment from a sectional flask separablealong a horizontal plane and having a bottom for one section providedwith a holding element from which the remainder of said section isremovable, comprising a stripper frame having a base and uprights risingfrom said base and positioned at opposite sides of said flask, and aclamping element above said flask bearing against said hold-- ingelement to retain the same and said investment in fixed position on saidbase, said uprights having means to serve as fulcrums for pryingelements adapted for engagement with the sections of said flask to stripthe same from said investment while retaining said holding elementagainst the latter.

7. A device for removing an investment from a sectional flask separablealong a horizontal plane and having a bottom for one section providedwith a holding element from which the remainder of said section isremovable, comprising a stripper frame having a base, uprights risingfrom said base at opposite sides of said flask and provided withopenings, a cross bar connecting said uprights and extending across theflask with clearance space between the latter and said cross bar and apressure device carried by said cross bar and exerting pressuredownwardly against said holding element whereby said investment isclamped between said holding element and said base, said openings beingadapted to have prying bars exerted therethrough and fulcrumed thereinto engage a section of said flask and strip the major portion of thesame. from said investment and to separate said portion from saidholding element while moving said portion upwardly into' said clearancespace.

3. A device for removing an investment from a sectional dental flaskhaving a lower section provided with a bottom equipped with aninvestment-holding element from which the remainder of said section isremovable, and a second section adjoining said bottom'section and incontact therewith edge to edge, comprising a stripper frame in whichsaid flask is placed in inverted position, said frame having a base withan elevated portion of smaller dimension than the interior 7cross-sectional dimension of said flask against which the investment insaid flask bears, two uprights rising from said base at opposite sidesof said flask, each having an opening therein, a cross bar connectingsaid uprights in a plane and a holding device including a pressure screwcarried by said crossbar and bearing against said investment-holdingelement the Walls of said openings serving as fulcrums for pryingelements adapted to pry the lower section of said flask upward away fromsaid investment and from said investment-holding element and the uppersection downward around said elevated portion and free of saidinvestment.

9. A device for removing investments from sectional dental flasks,comprising holding means engaging the investment at the top and bottomto immovably retain the same and including means to fulcrum a pryingelement thereon for prying the sections of the flask apart while saidinvestment is immovably retained within said holding means.

EDMOND J. FRANWICK.

